LONDON — Britain on Thursday created the world's largest marine reserve by banning fishing around the U.K.-owned archipelago in the Indian Ocean — a cluster of 55 islands across that cover an area larger than California.

The move pleased environmentalists but angered exiled Chagos Islanders, who say it creates an obstacle to them returning home.

Foreign Secretary David Miliband said commercial fishing will be halted around the Chagos Islands to allow scientific research and the preservation of coral reefs and an estimated 60 endangered species.

The move will "double the global coverage of the world's oceans under protection," he said, adding that the area "offers great scope for research in all fields of oceanography, biodiversity and many aspects of climate change, which are core research issues for U.K. science."

His ministry insisted the move would not affect operations on the island of Diego Garcia, which Britain leases to the U.S. military for use as a base.

Conservation groups and scientists welcomed the move to protect waters around the islands, reputedly some of the world's cleanest ocean, and claimed it would become as important for research as the Great Barrier Reef or Galapagos Islands.

"Nearly three quarters of the planet’s surface is water, but surprisingly little of it is protected," Jay Nelson, director of the Global Ocean Legacy, said in a statement. "For more than a century we have had the foresight to protect the Grand Canyon and Yellowstone National Park on land, but only recently have we turned our attention to protecting similarly significant places in the sea."

210,000 square milesMiliband said the protected zone would cover 210,000 square miles of ocean, which is home to about 220 types of coral, 1,000 species of fish and 33 different seabirds.

Marine Resources Assessment Group

These sharks were illegally fished inside the Chagos Islands.

The area also provides a safe haven for dwindling populations of sea turtles and more than 175,000 pairs of breeding seabirds, the Pew Environment Group said.

The Chagos Environment Network — a coalition of ocean scientists — said the area will replace the Papahanaumokuakea Marine National Monument, in Hawaii, as the world's largest marine reserve.

Miliband said Britain has agreed to transfer control of the territory to Mauritius "when it is no longer needed for defense purposes," but has not specified any timeframe.

Under the terms of the lease of Diego Garcia, the U.S. military can remain on the island until at least 2036.

Halfway between Africa and Southeast Asia, the Chagos Islands have been frequently controversial for the British government.

The European Court of Human Rights is considering a long running appeal from Chagossians evicted from their homes to nearby Mauritius between 1967 and 1973 to make way for the military base. Islanders are seeking to return to their former homes.

"The creation of this marine reserve is a first step towards securing a better and sustainable future for the Chagos Islands," said Greenpeace activist Willie Mackenzie. "But this future must include securing justice for the Chagossian people and the closure and removal of the Diego Garcia military base."